Mechanisms underlying the developmental emergence of a complex learned motor program

Bird song is a complex behavior composed of multiple syllable types. In adult birds, each syllable is encoded by a distinct sequence of bursts in the premotor cortical area HVC. To understand how these sequences in HVC develop during vocal learning, we have recorded HVC neurons in juvenile zebra finches throughout vocal development. Early in vocal learning, neurons exhibited rhythmic (5-1 0 Hz), with different neurons active at different phases of the rhythm. As new syllables emerged, some neurons were shared across emerging syllable types, and the fraction of these shared neurons decreased over development. These results are generated by a rhythmic prototype motor sequence.